1. Field of the Invention
The present invention relates to a brushless motor, and more particularly, to a brushless motor for driving a washing machine for reducing oscillations and noise.
2. Description of Related Art
In general, a brushless motor rotates a rotor by alternating the direction of current flowing in a driving coil without a brush.
Referring to FIG. 1, a conventional brushless motor includes a stator and a rotor rotatably connected to the stator.
The stator includes a shaft holder 20 and a yoke 30 installed under the shaft holder 20. The shaft holder 20 is fixed to a frame 10, and has a hollow portion 20a in which a shaft 50 is inserted. A groove 50a is formed on the upper portion of the shaft 50. First and second bearings 15 and 16 are installed in the shaft holder 20, and a receiving groove 20b is formed on the upper portion of the shaft holder 20. A washer 55 which fits in the groove 50a of the shaft 50 is installed in the receiving groove 20b to rest on the first bearing 15. Accordingly, the shaft 50 can be rotatably supported by means of the first and second bearings 15 and 16 without deviating downwards along the shaft axis. The yoke 30 connected to the shaft holder 20 is wound with a coil (not shown) so that a magnetic field is generated when current is applied to the coil.
The rotor includes the shaft 50 which is rotatably supported by the shaft holder 20, and a housing 60 which is connected to the bottom of the shaft 50, through a connecting portion 65, and which surrounds the yoke 30. A magnet 70 is disposed on the inner circumferential surface of the housing 60, spaced apart from the yoke 30 so that it can magnetically cooperate with the yoke 30.
In the above-described brushless motor, when an alternating current is applied to the coil surrounding the yoke 30, a magnetic field is generated which cooperates with the magnet to rotate the rotor with respect to the stator.
However, when the rotor operates for a long time, the shape of the washer 55 supporting the shaft 50 deforms causing the rotor to rotate off center and oscillate or generate noise.
Furthermore, if the rotor is heavy, the washer 55 can break, thereby permitting the rotor to deviate from its proper position in the stator.